This invention relates to improvements in read/write heads, and, in particular, to such heads having means for reducing the feedthrough signal induced in the read transducer from operation of the write transducer.
It has been well known in prior art in the magnetic recording system that recording and reproducing head means is provided to transmit to a recording medium and record information or intelligence on the medium and thereafter reproduce the recorded information. In a well-known apparatus for both recording and reproducing information, one pole piece may be provided and having a gap used for the purposes of both recording and reproducing. But there are disadvantages, such as, head life, handling operation, etc. because the immediate reproducing of a previously made record for checking purposes cannot be performed simultaneously while a new recording is being written or reproduced on the recording medium.
Recently, there has been employed a magnetic head having a two gap head arrangement in which the write pole-piece of the head preceeds the read pole-piece in the direction of motion of the magnetic recording medium. Accordingly, the intelligence recorded or written by the write pole-piece can be immediately reproduced or read out by the read pole-piece, so that the recording and reading of the intelligence for the purpose of checking for accuracy can be simultaneously performed.
In the two gap head assembly, read pole-piece and write pole-piece must be placed in very close proximity to each other in a single assembly. In order to reduce the "feedthrough" signal induced in the read pole-piece from the write pole-piece, a laminated mu-metal shield is placed in the head assembly between the write pole-piece and the read pole-piece. Furthermore, there may be provided a magnetic shield on the outside surface of the head assembly to reduce the stray magnetic field generated outside the head by the write pole-pieces and at the same time insuring the engagement between the magnetic tape and the gaps of the read and write pole-pieces.
The two gap head assembly as above described is not sufficient, however, in reducing feedthrough from the write pole-piece to the read pole-piece because gap areas of the read pole-piece and the write pole-piece must be exposed outside of magnetic shield means such as depicted in U.S. Pat. No. 3,479,662. When the motion speed of the magnetic medium relative to the head assembly is very great, the level of the read signal obtained from the read head is greater than the level of the feedthrough signal so that the feedthrough signal is not a significant disadvantage. But when the speed of the magnetic tape medium is relatively slower, the level of the read signal is nearly equal to the level of the feedthrough signal. Also the smaller the head assembly, the more ineffective is the magnetic shield to reduce the feedthrough signal, so that it is difficult to effectively reduce the feedthrough signal for different tape medium speed movements.